Alterations in performance and muscle composition of young turkeys in response to dietary amino acid balance.

Two experiments were performed to determine the effects of essential (EAA) and nonessential amino acid (NEAA) supplementation of a 22% protein corn-soybean meal diet on the performance of muscle composition of male Large White turkeys from 7 to 21 days of age. The 22% protein diet was supplemented with DL-methionine (MET) or a combination of MET and L-lysine (LYS) in Experiment 1. Additions in Experiment 2 included MET; and EAA mixture of MET, LYS, L-threonine, and L-valine; and a mixture of NEAA equal to 2% crude protein combined with either the MET or EAA supplement. Controls received a 30% protein diet. Each diet was fed ad libitum to five and four pens of eight poults in Experiment 1 and 2, respectively. Maximum performance was obtained with the 30% protein diet in both experiments. Methionine was confirmed as the first-limiting amino acid in the 22% protein diet. Lysine addition to the MET-supplemented low protein diet adversely affected performance in Experiment 1, suggesting that LYS was not the second most limiting amino acid. The EAA supplement elicited growth equal to the 30% protein diet although feed efficiency remained inferior. Increases in growth and feed efficiency were associated with NEAA addition. Changes in the weights of the pectoralis and gastrocnemius muscles due to diet, albeit directly related to body weight, were independent of muscle composition. The composition of gastrocnemius muscle was relatively insensitive to dietary manipulation. Pectoral ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) concentrations increased with a decrease in dietary protein. Amino acid supplementation reduced DNA concentration without altering muscle RNA.(ABSTRACT TRUNCATED AT 250 WORDS)